He regularly accompanied his father on various administrative duties and foreign trips, providing technical assistance and taking notes.

This started an interest in architectural matters, which he retained all his life, eventually becoming an accomplished civil architect.

During that time, he led the Chemical Department at King's College and carried out many studies on crystallisation and supersaturated solutions.

[4] Although he was much occupied with his own teaching and experimental work, Thomson was also a dedicated amateur photographer and actor with the Dramatic Society of King's College.

He taught the principles and practice of photography to the engineering students of the college and carried out experimental studies of photographic processes.

[3] Being the head of the Chemistry Department at King's College, in 1905, Thomson was offered the vacated post of vice-principal, which he held until retirement in 1914.